Emily Kavanaugh is standing in her skincare-product shop, Pure Nuff Stuff, on Chapel Street. The narrow lane leads down towards the Jubilee pool, the triangular lido that juts like a ship’s prow into the sea from Penzance. “Here, try one,” Kavanaugh says, handing me a piece of packing material. The little white cloud looks and feels like a polystyrene packing “peanut”, but, Kavanaugh assures me, “it tastes exactly like a communion wafer”. After a wary nibble, I pop the whole thing in and notch it up as a snack.

Kavanaugh’s packaging is made not of plastic but corn starch. If eating it feels like an act of faith, it is because there is a growing fervour in this Cornish seaside town. Last year, Penzance became the first town in Britain to receive “plastic-free” status from Surfers Against Sewage (SAS). The former single-issue movement, founded in Cornwall in 1990, has become a national marine conservation charity with plastics in its sights. But, rather than target shopping bags or plastic-lined coffee cups, SAS is attempting to unite whole communities against single-use plastic of all types, including straws, bottles, packaging, takeaway boxes, cotton buds, clingfilm and forks.

These were all items among the wretched flotsam that washed up on Cornish beaches in horrifying quantities when storms devastated the south-west coast in February 2014. Rachel Yates grew up in Penzance and remembers campaigning against CFCs as a child, but it was the aftermath of the storms that shook her into action as an adult after she joined an SAS beach-cleaning event. “There were bottles, cocktail sticks, coffee cup lids, razors, toothbrushes … I’d never seen anything like it and something in me snapped,” the 43-year-old radio journalist recalls.

Ocean plastics are more than a blight on pretty Cornish beaches. The UN has warned of the “irreparable damage” we are doing to marine life by discarding plastic, a lot of which ends up in the sea, toxifying food chains. The National Center for Ecological Analysis and Synthesis in California and the University of Georgia have estimated that up to 10m tonnes of plastic enter oceans each year. Last year, during a national clean-up of more than 300 beaches in Britain, the Marine Conservation Society found 718 pieces of litter, the majority of them plastic, for every 100-metre stretch of coastline.

“And it isn’t just a coastal issue – it’s everywhere,” says Yates. “I think more of us want to do something about it – something tangible and real.” Yates joined SAS and made it her mission to achieve plastic-free status for Penzance, according to criteria that the charity had been developing. Its five-point plan involves urging local government to change its behaviour and support the campaign; encouraging businesses to ditch single-use plastic; working with schools and youth groups; arranging events including plastic pickups; and creating a steering group to continue to grow the mission.

After a frantic few months of meetings, Yates secured plastic-free status for Penzance last December. Since then, more than 330 communities all over the country have applied to follow the town’s lead. So far, 29 have achieved the status, including Tynemouth in the north-east. They are all coastal, but the applicants include dozens of inland communities including Milton Keynes and Ripon. Why the flock of plastic-free aspirants and what has it meant for a town such as Penzance?

To start with, Yates beat a path to businesses that were already embracing a greener approach, including Kavanaugh’s store. Even in a shop with edible packaging, there were improvements to be made. Bath salts that had been sold in plastic tubs come in little paper bags. “Not long ago, my customers would be slightly sniffy about that, but I think attitudes are changing,” says Kavanaugh.

It’s a similar story round the corner at the Honey Pot, where Rachel Gunderson is preparing for the lunchtime rush. In the year that the 26-year-old has run the cafe, and signed up to the movement, she, too, has improved its environmental credentials. Plastic straws are banned and all the takeaway packaging, including coffee cups, is biodegradable. “I have also been challenging my suppliers,” Gunderson says. “I’ll order six aubergines and they’ll all come individually wrapped in plastic …”

Gunderson’s appeal to suppliers echoes the challenge of preaching to the unconverted. Consumer society has clingfilmed itself into a corner thanks to the near-magical qualities of an infinite range of plastics, whose use is baked into our supermarket economy. When Chepstow in south Wales celebrated its own SAS-approved plastic-free status last month, it did so with a huge plastic banner. If it looked as incongruous as a Peta ad printed on vellum, it only showed how woven into modern society plastic has become – for anyone wanting a durable, waterproof sign, there is nothing cheaper or more effective. (SAS pointed out that its campaign targets single-use plastic, not all plastic.)

Yates is determined to ensure that plastic-free communities are not just made up of people rewarding themselves for their own virtue, for which they are prepared and able to pay a premium. (Kavanaugh’s packaging costs tripled when she ditched plastic, some of which inevitably trickled down to customers.) She says that the numbers involved – more than 70 businesses have signed up in Penzance so far – and the conversations happening in the town show that the tide is turning, and that change need not be a luxury.

Paul Shaw runs Waves, an unassuming Penzance cafe behind an art deco facade. “I think that the public perception has turned considerably, even over the last 12 months, and they’re looking at this in a way they never did,” he says. He had been trying to do his bit, reusing large plastic tubs and ditching polystyrene takeaway boxes. But the plastic-free campaign inspired him to take a drastic step and refuse to serve takeout drinks to anyone without a reusable cup.

Shaw estimates that a quarter of his takeaway drinks customers stopped coming after the ban, costing him £2,600 a year in lost profits. “But is that what we need to do?” he asks. “I’m not pumping another load of crap into the system – I’m doing something to help.” Shaw is also convinced that the same move even two years ago would have been far more damaging to business. “Now, people are accepting that this is the way it needs to be.”

Everyone I talk to in Penzance has heard about the campaign, even if the outward signs are hard to spot (there is no plastic banner here). Support is real. Elizabeth Povey, who is on her way to the swimming pool when I accost her, says it is the talk of her quayside retirement home. “The only thing we don’t like is that we can’t recycle those black plastic ready-meal trays,” she says. “We’re stacking them up until someone works out what to do with them.” (Black plastic is recyclable, but machines can’t sort them because they can’t “see” the black pigment. Last month, Marks & Spencer, Tesco and Sainsbury’s announced they had plans to fix the problem.)

Almost without exception, residents and business owners cite one reason for the town’s fairly sudden unity around the plastic problem: Blue Planet II. By coincidence, the shocking final episode of the BBC documentary series, which showed albatross parents feeding their chicks plastic, aired last December, days before Penzance won its status. “We were already working on it and getting a phenomenal response, but I think Blue Planet really widened the awareness and made people want to do something,” Yates says.

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Lyndsey Dodds, head of marine policy at WWF, the conservation organisation says: “I have been working in marine science and policy for 20 years and I’ve never seen such an appetite for change or an interest in the marine environment.” Even if 1,000 communities ditching coffee cups were to have little effect on the nutrition of faraway albatross chicks, Dodds says the growing popular awareness that the SAS scheme harnesses could be powerful. “One town isn’t going to change the world, but it’s the groundswell that’s important,” she adds.

Not that scepticism is absent in Penzance. The guy behind the counter at Wharf House fish and chips, who preferred not to be named, opens a cupboard to reveal huge stacks of polystyrene takeaway boxes. He serves takeaway in paper when he can, but says it’s not always suitable. “And not everyone wants it,” he adds. Customers largely ignore the wooden forks he offers for a 5p surcharge. “It costs us more to get the wooden ones than plastic and we can’t afford to pass that on to the customers,” he says. His contract with a drinks supplier forbids him from adding cartons or glass bottles to the Coca-Cola fridge in the corner, which is filled with plastic bottles. He says the store supports the campaign, while falling some way short of acquiring a “plastic-free” sticker for his window. “But there is only so much we can do.”

Similar contractual binds inhibit progress elsewhere, too. When I meet Dick Cliffe, the mayor of Penzance, for a cold drink in the shade at the Orangery cafe at Penlee House, a council-run museum, he looks almost sheepish when he appears carrying two plastic bottles of water. “Unfortunately, the contract was renewed before the plastic-free status came in,” he says. He hopes the next contract will include a requirement to ditch plastic. The former RAF man otherwise preaches the plastic-free gospel, having led unanimous support for the campaign after Yates presented the council with the SAS plan.

“We didn’t get into this overnight, and we won’t get out of it overnight,” Kavanaugh says back at Pure Nuff Stuff. Even she still sells shampoos and other liquid products in plastic bottles because nothing else will do. As a member of the chamber of commerce here, and part of the plastic-free community steering committee, she is determined to take the fight up the food chain so that consumer organisation and pressure compels suppliers and other businesses to change practices, reducing the cost of doing the right thing.

She is in the process of talking to the 32 places in the town that sell coffee in an attempt to unite as many of them as possible into a cup-buying bloc to get a better price for biodegradable alternatives. “It’s about making it easier, so that it doesn’t cost an arm and a leg,” she says.

Rachel Yates now works for SAS on the national campaign to recruit more plastic-free communities. She’s under no illusion about the scale of the task. “Even in Penzance, we still have big chains giving out plastic cups and bags,” she says. “We can’t do this overnight, but you have to do it step by step; otherwise it’s too big to even think about. Hopefully, we’re laying the foundations for something really sustainable.”